The present invention relates generally to an apparatus and a method for separating sanitary effluent from storm water and/or infiltrated water in a municipal sewer system.
Municipal sewer systems include a web of pipes that convey wastewater from homes, businesses and industries and storm water from drains to treatment plants. The smallest pipes, typically twelve inches in diameter or less, are know as xe2x80x9ccollectorsxe2x80x9d that are connected to service lines running to the sanitary plumbing of buildings. The collectors are connected to xe2x80x9cmink linesxe2x80x9d, typically larger than twelve inches in diameter, and carrying one to ten million gallons per day. The trunk lines connect to xe2x80x9cinterceptorsxe2x80x9d that carry the wastewater to a treatment plant. The interceptors are of large diameter, often as much as ten feet.
The wastewater plumbing system in a typical house, office building or manufacturing facility combines toilet effluent with other wastewater, such as from sink and bath drains, to be carried by a single service line to the collector line at the street. Hereinafter, such combined wastewater will be termed xe2x80x9csanitary effluentxe2x80x9d. The municipal sewer systems combine and carry in the same pipes the sanitary effluent from buildings, storm water from outside drains and any ground water leaking into the system (infiltrated water). When the treatment plant and the associated web of pipes are built, the system is sized to process a predetermined number of gallons per unit of time, the maximum flow capacity, including a certain rainfall amount. As additional buildings are connected to the system, less of the predetermined flow capacity is available for storm water. Thus, the system becomes susceptible to rainfall amounts less than the planned certain rainfall amount causing numerous overflows into streams and lakes and backups into buildings through the service lines. Overflows also can occur in systems where the storm water is carried in a separate set of pipes. Such overflows and backups cause serious environmental and health problems.
Also, some sewer systems were designed with less capacity than is required to carry typical rainfall amounts thereby always overflowing during normal rainfalls. Typically, such systems were installed before there was much concern for the effect of the overflow on the environment.
However, no matter what the configuration of an existing sewer system, it either now has or will in the near future have flow capacity problems causing overflows, backups and leaks. Consequently, the local governments responsible for maintaining these sewer systems face enormous expenses to repair or replace the existing pipes and/or add capacity.
The present invention concerns an apparatus and method for improving the operation of sewer systems while reducing the cost of increasing system capacity. The apparatus according to the present invention includes a first set of sewer lines connected to at least one storm water drain, and/or source of infiltrated water, and/or source of sanitary effluent, and a second set of sewer lines of smaller diameter than said sewer lines of said first set connected to sources of sanitary effluent, the first and second sets of lines being separately connected to a sewerage treatment plant. The second set of sewer lines has at least a portion thereof that extends inside the first set of sewer lines and the first set of sewer lines can be an existing sanitary sewer system. The apparatus can include at least one sanitary effluent process device connected to the second set of sewer lines such as a pumping station, a grinder pump or a vacuum system to assist the flow of the sanitary effluent through the second set of sewer lines. The apparatus can provide the same flow volume in a smaller diameter pipe that is under pressure.
The method according to the present invention includes the steps of: a. providing a first set of sewer lines connected between at least one source of storm water, and/or source of infiltrated water, and/or source of sanitary effluent, and at least one sewerage treatment plant; b. providing a second set of sewer lines connected between a source of sanitary effluent and the sewerage treatment plant; and c. installing at least a portion of said second set of sewer lines in said first set of sewer lines. Step b. can include installing a sanitary effluent collector line spaced from a collector line of the first set of sewer lines and connecting a service line from the source of sanitary effluent to the sanitary effluent collector line. Step c. can include running the sanitary effluent collector line to a manhole associated with the collector line of the first set of sewer lines and connecting the sanitary effluent collector line to a portion of the second set of sewer lines installed in the first set of sewer lines. Step c. can be performed by in situ forming of pipe included in the second set of sewer lines.
A sewer system according to the present invention reduces the size of the pipe required to carry sanitary effluent and/or increases the capacity of the sewerage treatment plant to treat sanitary effluent. Since the storm water and infiltrated water are separated from the sanitary effluent, they may require little or no treatment freeing plant capacity to treat the sanitary effluent. In some cases, treatment plant expansion can be delayed or eliminated.